Abstract: For use in an alarm system, a security switch is provided, the transition state of which is detected by an associated circuit and a coded signal transmitted along a communication path indicative of the transition state, this coded signal being received and decoded to provide an output indication of the switch state.

Abstract: Line security apparatus for a direct-wire alarm system utilizes a transmitter at the remote premises to impose on the direct current a small amplitude carrier frequency which is on/off modulated by a clocked, continuous progression of pseudo-random digital bits. A receiver, tuned for the carrier frequency, is utilized at the monitoring station to recover the progression of digital bits, if received at the monitoring station. A microprocessor at the monitoring station produces an identical and initially synchronous sequence of digital bits, compares the produced sequence to the progression of bits received, and effects a temporary alarm signal indicating that the line security is disrupted if the bits do not correspond. Because the lack of correspondence may be due to deviations of the transmitter and microprocessor clocks, the microprocessor seeks correspondence by shifting the produced sequence and, if successful, continues the comparison as shifted.

Abstract: A security system for supervising the integrity of a communication line having a supervising apparatus which generates first and second random signals, compares these first and second randomly generated signals to provide a third signal and compares this third signal to a fourth signal, and a transponder, also connected to the line, which compares the first and second randomly generated signals to provide the fourth signal to the communication line. The use of randomly generated signals increases the difficulty of breaching line security such that, when the supervisory apparatus detects a difference between the third and fourth signals, it can provide an appropriate alarm, indication, or control.

Abstract: A security system for supervising the integrity of a communication line having a supervising apparatus which generates first and second random signals, compares these first and second randomly generated signals to provide a third signal and compares this third signal to a fourth signal, and a transponder, also connected to the line, which compares the first and second randomly generated signals to provide the fourth signal to the communication line. The use of randomly generated signals increases the difficulty of breaching line security such that, when the supervisory apparatus detects a difference between the third and fourth signals, it can provide an appropriate alarm, indication, or control.

Abstract: A multiple sensor intrusion alarm system including a central controller which communicates with a plurality of sensors over a single, interconnecting cable. The controller periodically polls each of the sensors, and in response to this polling signal, each sensor returns a signal indicating its status. The absence of a return signal from a particular sensor indicates to the controller that the sensor is malfunctioning or has been tampered with. In a preferred embodiment, the interconnecting cable is a single, two-conductor cable. The controller may also be connected to an alarm panel or remote monitoring station to indicate the presence of an alarm condition.

Abstract: An automatic washing machine which automatically carries out the steps of washing, rinsing and dehydrating in accordance with a preselected program, comprises an indication means for indicating the occurrence of abnormal operation if it occurs in the steps of washing, rinsing and dehydrating, in such a manner that the indication mode differs from cause to cause of the occurrence of the abnormal operation.

Abstract: A selected predetermined coded alarm is provided indicative of the one of a plurality of leads on which a signal indicative of an alarm condition may appear. If a station coded alarm should be initiated during the transmission of a coded alarm, the coded alarm is immediately terminated and the station coded alarm is given priority and transmitted immediately. Upon completion of the station coded alarm, the coded alarm being transmitted at the time of the receipt of the station coded alarm is transmitted with the new transmission starting at the start of its code irrespective of the status of the transmission at the time of the interruption. Appropriate delays are provided between codes and code elements. The plurality of leads are sequentially scanned, but once a transmitted code is transmitted, it is not retransmitted on a subsequent scan unless a reset signal has been provided. Each transmitted code is repeated a predetermined number of times.